Polyimide and doped metal oxide intermediate transfer components

ABSTRACT

A polyimide film component useful in intermediate transfer, bias transfer, and transfix applications, the polyimide film having electrically conductive doped metal oxide fillers dispersed therein, the polyimide film having a surface resistivity of from about 10 6  to about 10 14  ohm/sq, and optionally provided on the polyimide film an outer layer, or in the following order both a conformable intermediate layer and an outer release layer.

Attention is directed to copending application Attorney Docket No.D/95609 U.S. patent application Ser. No. 09/004,554 filed Jan. 08, 1998entitled, "Polyimide and Doped Metal Oxide Fuser Components;" AttorneyDocket No. D/95609Q1 U.S. patent application Ser. No. 09/004,209, filedJan. 08, 1998, entitled, "Haloelastomer and Doped Metal OxideCompositions," Attorney Docket No. D/9560902, U.S. patent applicationSer. No. 09/004,421, filed Jan. 08, 1998, entitled, "Haloelastomer andDoped Metal Oxide Film Components," and Attorney Docket No. D/9560904,U.S. patent application Ser. No. 09/004,492, filed Jan. 08, 1998,entitled, "Polyurethane and Doped Metal Oxide Film Components." Theseapplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to an imaging apparatus and filmcomponents thereof for use in electrostatographic apparatuses. The filmcomponents herein are useful for many purposes including removing tonerfrom a charge retentive surface and transporting it to a final imagesubstrate, transferring toner from a charge retentive surface to a biascharging member, and in transfuse applications wherein the toner istransferred and fused to a copy substrate. More specifically, thepresent invention relates to film components comprising a high moduluspolyimide which, in embodiments, is filled with a conductive filler inorder to impart a desired resistivity. In specific embodiments, theconductive filler is a doped metal oxide filler, preferably antimonydoped tin oxide filler. In another embodiment, the film componentscomprise a polyimide substrate, and an outer conformable layer providedthereon. In yet another embodiment, the film components comprise apolyimide substrate, an intermediate conformable/electrical layerprovided thereon, and an outer release layer provided on theconformable/electrical layer. The present invention may be useful inxerographic machines for various applications, especially for colorapplications.

Examples of suitable film components include intermediate transfermembers such as those described in Buchan et al., U.S. Pat. No.3,893,761, which discloses an intermediate transfer belt having apolyimide film substrate coated with 0.1 to 10 mils of silicone rubberor a fluoroelastomer. Berkes et al., U.S. Pat. No. 5,119,140, disclosesa single layer intermediate transfer belt fabricated from clear Tedlar®,carbon loaded Tedlar® or pigmented Tedlar®. Nisheise et al., U.S. Pat.No. 5,099,286, discloses an intermediate transfer belt comprisingelectrically conductive urethane rubber as the substrate (10³ to 10⁴ohm-cm) and a layer of polytetrafluoroethylene. Bujese, U.S. Pat. No.5,150,161, discloses suitable materials for laminate intermediatetransfer members in a color printing apparatus. Bujese et al., U.S. Pat.No. 5,208,638, discloses an intermediate transfer surface employing aconductive fluoropolymer material. Mammino et al., U.S. Pat. No.5,298,956, discloses a reinforced seamless intermediate transfer memberhaving embedded in the reinforcing member, filler materials and anelectrical property regulating material.

Yu et al., U.S. Pat. No. 5,303,014, discloses a bias transfer membercomprising a layer of resistive material (10¹⁰ to 10¹⁵ ohms-cm) such aspolyimide siloxane and polytetrafluoroethylene having fluorine atomsembedded therein. Eddy et al., U.S. Pat. No. 3,959,573 disclosesbiasable members having at least one layer of coating of a hydrophobicelastomeric polyurethane. Similarly, Seanor et al., U.S. Pat. No.3,929,574 discloses biasable members having an elastomeric resilientpolyurethane coating filled with ionic additives.

U.S. Pat. No. 5,576,818 discloses an intermediate transfer componenthaving multiple coatings including a) an electrically conductivesubstrate, b) a conformable and electrically resistive layer comprisedof a first polymeric material, and c) a toner release layer comprised ofa second polymeric material. The substrate may be polyimide filled withcarbon black, the intermediate layer may be fluoroelastomer, and theouter release layer may be a fluoroelastomer or fluorosilicone. U.S.Pat. No. 5,612,773 discloses a transfix configuration for a colorapparatus.

It is desirable to provide a multifunctional transfer film that can besuitable for use in several areas in the electrostatographic transferprocess such as intermediate transfer, bias transfer, and transfix. Itis also desirable to provide such a film for use in liquid developmentproduction color machine employing image-on image technology.

For such a multifunctional transfer film component, it is necessary toimpart conductive properties to such films by addition of conductivefillers. Carbon black has been the chosen additive for impartingconductive properties in electrostatographic films. Carbon black isrelatively inexpensive and very efficient in that a relatively smallpercentage can impart a high degree of conductivity. However, theblackness of this material makes it difficult and sometimes impossibleto fabricate colored products with the desired level of conductivity.Further, films filed with carbon black have a tendency to slough andthereby contaminate their surroundings with black, conductive debris.

Many doped metal oxides offer significant advantages in both color andtransparency when compared to carbon black. They are, however,relatively expensive and usually require higher dosages to achievecomparable levels of conductivity. In addition, dispersion of metaloxides can lead to short comings in surface roughness and particle size.

Therefore, a need remains for conductive films for use inelectrostatographic machines, wherein the film possesses desiredresistivity without the drawbacks of lack of transparency of the filmwhich may adversely affect use in color products. Further, a needremains for a conductive film having conductive fillers which impart thedesired resistivity without compromising surface roughness. Further, aneed remains for films having improved mechanical properties to maintainfilm or belt integrity for improved flex life and image registration,improved electrical properties including a resistivity within the rangedesired for superior performance and to control electrostatic transferfunctions, improved chemical stability to liquid developer or toneradditives, improved thermal stability for transfix operations, improvedconformability, low surface energy, and higher modulus. Further, a needexists for a film in which the resistivity is uniform and is relativelyunaffected by changes in environmental conditions such as changes inhumidity, temperature, electrical surges, and the like. Many of theseobjects have been met by embodiments of the present invention.

SUMMARY OF THE INVENTION

The present invention provides, in embodiments, a transfer filmcomponent comprising a polyimide film and electrically conductive dopedmetal oxide fillers dispersed therein, wherein said polyimide film has asurface resistivity of from about 10⁶ to about 10¹⁴ ohm/sq.

The present invention further provides, in embodiments, a bias transfermember for use in an electrostatographic printing apparatus fortransferring electrically charged particles from an image supportsurface to said biasable transfer member, wherein said biasable transfermember comprises a polyimide film and electrically conductive dopedmetal oxide fillers dispersed therein, wherein said polyimide film has asurface resistivity of from about 10⁶ to about 10¹⁴ ohm/sq.

Additionally, the present invention includes, in embodiments, an imageforming apparatus for forming images on a recording medium comprising: acharge-retentive surface to receive an electrostatic latent imagethereon; a development component to apply toner to said charge-retentivesurface to develop said electrostatic latent image to form a developedimage on said charge retentive surface; a transfer film component totransfer the developed image from said charge retentive surface to acopy substrate; said transfer film component comprising a polyimide filmsubstrate and electrically conductive doped metal oxide fillersdispersed therein, wherein said polyimide film has a surface resistivityof from about 10⁶ to about 10¹⁴ ohm/sq.

Moreover, present invention further provides, in embodiments, an imageforming apparatus for forming images on a recording medium comprising: acharge-retentive surface to receive an electrostatic latent imagethereon; a development component to apply toner to said charge-retentivesurface to develop said electrostatic latent image to form a developedimage on said charge retentive surface; a bias transfer film componentfor transferring electrically charged particles from said chargeretentive surface to said bias transfer film component, wherein saidbias transfer film component comprises a polyimide film substrate andelectrically conductive doped metal oxide fillers dispersed therein,wherein said polyimide film has a surface resistivity of from about 10⁶to about 10¹⁴ ohm/sq.

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects of the present invention will become apparent as thefollowing description proceeds upon reference to the drawings in which:

FIG. 1 is a schematic illustration of an image apparatus in accordancewith the present invention.

FIG. 2 is a schematic illustration of an embodiment of the presentinvention, and represents a transfer belt in accordance with the presentinvention having a one layer configuration.

FIG. 3 is an illustration of an embodiment of the present invention, andrepresents a transfer belt in accordance with the present inventionhaving a two layer configuration.

FIG. 4 is an illustration of an embodiment of the present invention, andrepresents a transfer belt in accordance with the present inventionhaving a three layer configuration.

FIG. 5 is an illustration of an embodiment of the present invention, andrepresents a transfix belt having a one layer configuration.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to film components which include biastransfer, intermediate transfer, transfix components, and the like. Inone embodiment of the present invention, the transfer film componentcomprises a substrate which comprises a polyimide having electricallyconductive doped metal oxide fillers dispersed therein. In anotherembodiment, the film component comprises a polyimide substrate havingelectrically conductive doped metal oxide fillers dispersed therein, andan outer conformable layer provided thereon. In still anotherembodiment, the present invention relates to a film component comprisinga polyimide substrate having electrically conductive doped metal oxideparticles dispersed therein, an intermediate conformable/electricallayer provided on the polyimide substrate, and an outer release layerprovided on the electrical/conformable intermediate layer.

Referring to FIG. 1, in a typical electrostatographic reproducingapparatus, a light image of an original to be copied is recorded in theform of an electrostatic latent image upon a photosensitive member andthe latent image is subsequently rendered visible by the application ofelectroscopic thermoplastic resin particles which are commonly referredto as toner. Specifically, photoreceptor 10 is charged on its surface bymeans of a charger 12 to which a voltage has been supplied from powersupply 11. The photoreceptor is then imagewise exposed to light from anoptical system or an image input apparatus 13, such as a laser and lightemitting diode, to form an electrostatic latent image thereon.Generally, the electrostatic latent image is developed by bringing adeveloper mixture from developer station 14 into contact therewith.Development can be effected by use of a magnetic brush, powder cloud, orother known development process. A dry developer mixture usuallycomprises carrier granules having toner particles adheringtriboelectrically thereto. Toner particles are attracted from thecarrier granules to the latent image forming a toner powder imagethereon. Alternatively, a liquid developer material may be employed,which includes a liquid carrier having toner particles dispersedtherein. The liquid developer material is advanced into contact with theelectrostatic latent image and the toner particles are deposited thereonin image configuration.

After the toner particles have been deposited on the photoconductivesurface, in image configuration, they are transferred to a copy sheet 16by transfer means 15, which can be pressure transfer or electrostatictransfer. Alternatively, the developed image can be transferred to anintermediate transfer member, or bias transfer member, and subsequentlytransferred to a copy sheet. Examples of copy substrates include paper,transparency material such as polyester, polycarbonate, or the like,cloth, wood, or any other desired material upon which the finished imagewill be situated.

After the transfer of the developed image is completed, copy sheet 16advances to fusing station 19, depicted in FIG. 1 as fuser belt 20 andpressure roll 21 (although any other fusing components such as fuserroll in contact with a pressure roll, fuser roll in contact withpressure belt, and the like, are suitable for use with the presentapparatus), wherein the developed image is fused to copy sheet 16 bypassing copy sheet 16 between the fusing and pressure members, therebyforming a permanent image. Alternatively, transfer and fusing can beeffected by a transfix application.

Photoreceptor 10, subsequent to transfer, advances to cleaning station17, wherein any toner left on photoreceptor 10 is cleaned therefrom byuse of a blade (as shown in FIG. 1), brush, or other cleaning apparatus.

The transfer film component employed for the present invention can be ofany suitable configuration. Examples of suitable configurations includea sheet, a film, a web, a foil, a strip, a coil, a cylinder, a drum, anendless mobius strip, a circular disc, a belt including an endless belt,an endless seamed flexible belt, an endless seamless flexible belt, anendless belt having a puzzle cut seam, and the like.

The transfer film components of the instant invention may be employed ineither an image on image transfer or a tandem transfer of a tonedimage(s) from the photoreceptor to the intermediate transfer component,or in a transfix system for simultaneous transfer and fusing thetransferred and developed latent image to the copy substrate. In animage on image transfer, the color toner images are first deposited onthe photoreceptor and all the color toner images are then transferredsimultaneously to the intermediate transfer component. In a tandemtransfer, the toner image is transferred one color at a time from thephotoreceptor to the same area of the intermediate transfer component.

Transfer of the developed image from the imaging member to theintermediate transfer element and transfer of the image from theintermediate transfer element to the substrate can be by any suitabletechnique conventionally used in electrophotography, such as coronatransfer, pressure transfer, bias transfer, and combinations of thosetransfer means, and the like. In the situation of transfer from theintermediate transfer medium to the substrate, transfer methods such asadhesive transfer, wherein the receiving substrate has adhesivecharacteristics with respect to the developer material, can also beemployed. Typical corona transfer entails contacting the deposited tonerparticles with the substrate and applying an electrostatic charge on thesurface of the substrate opposite to the toner particles. A single wirecorotron having applied thereto a potential of between about 5,000 andabout 8,000 volts provides satisfactory transfer. In a specific process,a corona generating device sprays the back side of the image receivingmember with ions to charge it to the proper potential so that it istacked to the member from which the image is to be transferred and thetoner powder image is attracted from the image bearing member to theimage receiving member. After transfer, a corona generator charges thereceiving member to an opposite polarity to detach the receiving memberfrom the member that originally bore the developed image, whereupon theimage receiving member is separated from the member that originally borethe image.

For color imaging, typically, four image forming devices are used. Theimage forming devices may each comprise an image receiving member in theform of a photoreceptor of other image receiving member. Theintermediate transfer member of an embodiment of the present inventionis supported for movement in an endless path such that incrementalportions thereof move past the image forming components for transfer ofan image from each of the image receiving members. Each image formingcomponent is positioned adjacent the intermediate transfer member forenabling sequential transfer of different color toner images to theintermediate transfer member in superimposed registration with oneanother.

The intermediate transfer member moves such that each incrementalportion thereof first moves past an image forming component and comesinto contact with a developed color image on an image receiving member.A transfer device, which can comprise a corona discharge device, servesto effect transfer of the color component of the image at the area ofcontact between the receiving member and the intermediate transfermember. In a like fashion, image components of colors such as red, blue,brown, green, orange, magenta, cyan, yellow and black, corresponding tothe original document also can be formed on the intermediate transfermember one color on top of the other to produce a full color image.

A transfer sheet or copy sheet is moved into contact with the tonerimage on the intermediate transfer member. A bias transfer member may beused to provide good contact between the sheet and the toner image atthe transfer station. A corona transfer device also can be provided forassisting the bias transfer member in effecting image transfer. Theseimaging steps can occur simultaneously at different incremental portionsof the intermediate transfer member. Further details of the transfermethod employed herein are set forth in U.S. Pat. No. 5,298,956 toMammino, the disclosure of which is hereby incorporated by reference inits entirety.

The intermediate transfer member herein can be employed in variousdevices including, but not limited to, devices described in U.S. Pat.Nos. 3,893,761; 4,531,825; 4,684,238; 4,690,539; 5,119,140; and5,099,286; the disclosure of all of which are hereby incorporated byreference in their entirety.

Bias transfer is another method of effecting transfer of a developedimage from one member to another. The process of transferring tonermaterials via a bias transfer system in an electrostatographic apparatusinvolves the physical detachment and transfer over of chargedparticulate toner material from a first image support surface (i.e., aphotoreceptor) into attachment with a second image support substrate(i.e., a copy sheet or intermediate transfer member) under the influenceof electrostatic force fields generated by an electrically biased memberand charge being deposited on the second image support substrate by, forexample, a bias transfer belt or film or roll, or by spraying the chargeon the back of the substrate. The bias transfer films are configured soas to include an inner conductive member having at least one layer ofhigh electrical resistance material, for transferring a toner powderimage from the photoreceptor onto a print receiving web, for chargingthe back side of a substrate, or charging the photoreceptor prior to theexposure of the original document to form an electrostatic latent imageon the photoreceptor. Further data concerning bias roll transfer methodsis provided in, for example, U.S. Pat. No. 3,847,478, U.S. Pat. No.3,942,888, and U.S. Pat. No. 3,924,943, the disclosures of each of whichare totally incorporated herein by reference.

Transfer and fusing may occur simultaneously in a transfixconfiguration. As shown in FIG. 5, a transfer apparatus 15 is depictedas transfix belt 4 being held in position by driver rollers 22 andheated roller 2. Heated roller 2 comprises a heater element 3. Transfixbelt 4 is driven by driving rollers 1 in the direction of arrow 8. Thedeveloped image from photoreceptor 10 (which is driven in direction 7 byrollers 1) is transferred to transfix belt 4 when contact withphotoreceptor 10 and belt 4 occurs. Pressure roll 5 aids in transfer ofthe developed image from photoreceptor 10 to transfix belt 4. Thetransferred image is subsequently transferred to copy substrate 16 andsimultaneously fixed to copy substrate 16 by passing the copy substrate16 between belt 4 (containing the developed image) and pressure roll 9.A nip is formed by heated roll 2 with heating element 3 containedtherein and pressure roll 9. Copy substrate 16 passes through the nipformed by heated roll 2 and pressure roll 9, and simultaneous transferand fusing of the developed image to the copy substrate 16 occurs.

An important aspect of the transfer process focuses on maintaining thesame pattern and intensity of electrostatic fields as on the originallatent electrostatic image being reproduced to induce transfer withoutcausing scattering or smearing of the developer material. This importantand difficult criterion is satisfied by careful control of theelectrostatic fields, which, by necessity, should be high enough toeffect toner transfer while being low enough to not cause arcing orexcessive ionization at undesired locations. These electricaldisturbances can create copy or print defects by inhibiting tonertransfer or by inducing uncontrolled transfer which can easily causescattering or smearing of the development materials.

In the pretransfer air gap region, or the so-called prenip regionimmediately in advance of copy sheet contact with the image, excessivelyhigh transfer fields can result in premature toner transfer across theair gap, leading to decreased resolution or blurred images. Hightransfer fields in the prenip air gap can also cause ionization, whichmay lead to loss of transfer efficiency, strobing or other imagedefects, and a lower latitude of system operating parameters.Conversely, in the post transfer air gap region or the so-called postnipregion at the photoconductor-copy sheet separation area, insufficienttransfer fields can give rise to image dropout and may generate hollowcharacters. Improper ionization in the postnip region may also createimage stability defects and can give rise to copy sheet separationproblems. One overriding consideration is providing an effectivetransfer system that focuses on the transfer field generated in thetransfer region which must be maximized in the area directly adjacentthe transfer nip where the copy paper contacts the image so that hightransfer efficiency and stable transfer can be achieved. Therefore,acceptable transfer field by controlling the resistivity range at thepre and post nip areas is important for effective transfer.

The polyimide film as the substrate in the above transfer configurationsof the present invention can be any suitable high elastic moduluspolyimide capable of becoming a conductive film upon the addition ofelectrically conductive particles. A polyimide having a high elasticmodulus is preferred because the high elastic modulus optimizes the filmstretch registration and transfer or transfix conformance. The polyimideused herein has the advantages of improved flex life and imageregistration, chemical stability to liquid developer or toner additives,thermal stability for transfix applications and for improved overcoatingmanufacturing, improved solvent resistance as compared to knownmaterials used for film for transfer components, and improved electricalproperties including a uniform resistivity within the desired range.Suitable polyimides include those formed from various diamines anddianhydrides, such as poly(amide-imide), polyetherimide, siloxanepolyetherimide block copolymer such as, for example, SILTEM STM-1300available from General Electric, Pittsfield, Mass., and the like.Preferred polyimides include aromatic polyimides such as those formed bythe reacting pyromellitic acid and diaminodiphenylether sold under thetradename KAPTON®-type-HN, available from DuPont. Another suitablepolyimide available from DuPont and sold as KAPTON®-Type-FPC-E, isproduced by imidization of copolymeric acids such asbiphenyltetracarboxylic acid and pyromellitic acid with two aromaticdiamines such as p-phenylenediamine and diaminodiphenylether. Anothersuitable polyimide includes pyromellitic dianhydride and benzophenonetetracarboxylic dianhydride copolymeric acids reacted with 2,2-bis4-(8-aminophenoxy)phenoxy!-hexafluoropropane available as EYMYD typeL-20N from Ethyl Corporation, Baton Rouge, La. Other suitable aromaticpolyimides include those containing 1,2,1',2'-biphenyltetracarboximideand para-phenylene groups such as UPILEX®-S available from UniglobeKisco, Inc., White Planes, N.Y., and those havingbiphenyltetracarboximide functionality with diphenylether end spacercharacterizations such as UPILEX®-R also available from Uniglobe Kisco,Inc. Mixtures of polyimides can also be used.

In a preferred embodiment, the polyimide is subjected to fluorine gas toproduce a fluorinated polyimide film. This treatment reduces the surfaceenergy.

The polyimide is present in the film in an amount of from about 60 toabout 99.9 percent by weight of total solids, preferably from about 80to about 90 percent by weight of total solids. Total solids as usedherein includes the total percentage by weight of polymer, conductivefillers and any additives in the layer.

The film component of the present invention may be in the form of anonconformable transfer or transfix component. In this embodiment asshown in FIG. 2, the transfer or transfix component is in the form offilm 24 comprising a polyimide layer 30 having electrically conductivedoped metal oxide fillers 31 dispersed therein. The single layer filmpreferably has a thickness of from about 10 to about 125 μm, preferablyfrom about 50 to about 100 μm. This non-conformable layer has a modulusof from about 300,000 PSI to about 1.5 million PSI.

The one-layer film herein, preferably in the form of a belt, has awidth, for example, of from about 300 to about 2,000 mm, preferably fromabout 300 to about 900 mm. The circumference of the non-conformable filmis from about 500 to about 3,600 mm, preferably from about 525 to about1,100 mm.

The one layer film member may be prepared by preparation of thepolyimide, for example, by using the reaction product of a diamine witha dianhydride dissolved in a solvent such as N-methyl-2-pyrrolidone. Anappropriate amount of filler is then added and dispersed therein inorder to provide a surface resistivity of from about 10⁴ to about 10¹²,preferably from about 10⁶ to about 10¹², and particularly preferred offrom about 10⁸ to about 10¹¹ ohms/sq. The filler is added and themixture is pebble milled in a roller mill, attritor or sand mill. Thepoly(amic acid) filler mixture is cast onto a surface, the solventremoved by evaporation and heated to convert the poly(amic acid) topolyimide. After addition of the filler particles, the polyimide layermay be formed by extrusion into a sheet or into an endless loop by knownmethods. If not, the two ends of the member can be joined by heat orpressure and the resulting seam can be coated with an adhesive fillermaterial and/or sanded to produce a seamless component by mechanicaldevices such as a pad or roller with single or multiple grades orabrasive surfaces, a skid plate, electronic laser ablation mechanism orchemical treatment as practiced in the art. In a preferred embodiment ofthe invention, the film is in the form of an endless seamed or seamlessbelt. The seam may impart a puzzle cut configuration as described inU.S. Pat. Nos. 5,487,707; 5,514,436; and U.S. patent application Ser.No. 08/297,203 filed August 29, 1994, the disclosures each of which areincorporated herein by reference in their entirety. A method formanufacturing reinforced seamless belts is set forth in U.S. Pat. No.5,409,557, the disclosure of which is hereby incorporated by referencein its entirety.

In another embodiment of the invention as shown in FIG. 3, the transferor transfix component is in the form of film 24 of a two layerconfiguration. The transfer component 24 comprises a polyimide substratelayer 30 having electrically conductive doped metal oxide fillers 31dispersed therein. An outer layer 32 is positioned on the polyimidesubstrate layer 30. The substrate imparts mechanical strength and theouter layer imparts conformability to a wide range of toner pile heightsfor superior transfer.

Preferred materials for the outer layer 32 include relatively lowsurface energy materials such as fluoropolymers such aspolytetrafluoroethylene (PTFE), fluorinated ethylenepropylene copolymer(FEP), polyfluoroalkoxypolytetrafluoroethylene (PFA Teflon) and otherTEFLON®-like materials; silicone materials such as fluorosilicones andsilicone rubbers such as silicone rubber 552, available from SampsonCoatings, Richmond, Va., (polydimethyl siloxane/dibutyl tin diacetate,0.45 g DBTDA per 109 grams polydimethyl siloxane rubber mixture, withmolecular weight of approximately 3,500); polyimides such as PAI(polyamide imide), Pl (polyimide), polyaramide, polyphthalamide, andthose polyimides sold under the tradename KALREZ® available from DuPont;and fluoroelastomers such as those sold under the tradename VITON® suchas copolymers and terpolymers of vinylidenefluoride, hexafluoropropyleneand tetrafluoroethylene, which are known commercially under variousdesignations as VITON A®, VITON E®, VITON E60C®, VITON E45®, VITONE430®, VITON B 910®, VITON GH®, VITON B50®, VITON E45®, and VITON GF®.The VITON® designation is a Trademark of E.I. DuPont de Nemours, Inc.Two preferred known fluoroelastomers are (1) a class of copolymers ofvinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, knowncommercially as VITON A®, (2) a class of terpolymers ofvinylidenefluoride, hexafluoropropylene and tetrafluoroethylene knowncommercially as VITON B®, and (3) a class of tetrapolymers ofvinylidenefluoroide, hexafluoropropylene, tetrafluoroethylene and a curesite monomer. VITON A®, and VITON B®, and other VITON® designations aretrademarks of E.I. DuPont de Nemours and Company. In another preferredembodiment, the fluoroelastomer is a tetrapolymer having a relativelylow quantity of vinylidenefluoride. An example is VITON GF®, availablefrom E.I. DuPont de Nemours, Inc. The VITON GF® has 35 mole percent ofvinylidenefluoride, 34 mole percent of hexafluoropropylene and 29 molepercent of tetrafluoroethylene with 2 percent cure site monomer. Thecure site monomer can be those available from DuPont such as4-bromoperfluorobutene-1,1,1-dihydro-4-bromoperfluorobutene-1,3bromoperfluoropropene-1,1,1-dihydro-3-bromoperfluoropropene-1, or any other suitable, known,commercially available cure site monomer.

The polyimide substrate layer of the two layer configuration has theproperties as described above for the one layer configuration. The outerlayer of the two layer configuration has a hardness of from about 50 toabout 80 Shore A, preferably from about 60 to about 70 Shore A. Thethickness of the outer layer is from about 2 to about 1500 μm,preferably from about 75 to about 500 μm.

The outer layer is coated on the substrate in any suitable known manner.Typical techniques for coating such materials on the reinforcing memberinclude liquid and dry powder spray coating, dip coating, wire wound rodcoating, fluidized bed coating, powder coating, electrostatic spraying,sonic spraying, blade coating, molding, laminating, and the like. It ispreferred to spray or flow coat the outer material when the thicknessdesired is about 125 μm.

In a third embodiment as depicted in FIG. 4, the transfer or transfixcomponent is in the form of film 24 of a three layer configuration andcomprises a polyimide substrate 30 having a electrically conductivedoped metal oxide fillers 31 dispersed therein, an intermediate layer 33(preferably a conformable layer) and an outer layer release layer 34provided on the intermediate layer 33. Preferably, the intermediatelayer 33 comprises a conformable material having a hardness of fromabout 40 to about 90 Shore A, preferably from about 50 to about 60 ShoreA; a thickness of from about 75 to about 2000 μm, and preferably fromabout 125 to about 1500 μm; with electrical properties similar to thesubstrate material. The intermediate layer preferably has requirementsthat it is able to adhere both to the outer layer and to the substratematerial. Materials suitable for the intermediate layer include siliconerubbers as set forth above, fluoroelastomers as described above,urethane nitrites, ethylene diene propene monomers (EPDM), conformablefluoropolymers as described above, other high surface energy materials,and any other material capable of meeting the temperature andconformability requirements. The substrate and outer layer are asdescribed above for the substrate and outer layers for the two layerconfiguration. This three layer configuration provides superiorconformability and is suitable for use in color xerographic machines.

In the three layer configuration, the substrate polyimide layer has theproperties as described above.

The polymers of the intermediate and outer layers of the three layerconfiguration are preferably present in the respective layers in anamount of from about 60 to about 99.9 percent, and preferably from about80 to about 90 percent by weight of total solids.

The transfer or transfix film employs electrically conductive particlesdispersed in the polyimide film. These electrically conductive particlesdecrease the base material resistivity into the desired surfaceresistivity range of from about 10⁶ to about 10¹⁴, preferably from about10⁸ to about 10¹³, and more preferably from about 10¹⁰ to about 10¹³ohms-sq. The desired volume resistivity is from about 10⁵ to about 10¹³,preferably from about 10⁷ to about 10¹¹ ohm-cm. The desired resistivitycan be provided by varying the concentration of the conductive filler.It is important to have the resistivity within this desired range. Thetransfer film component will exhibit undesirable effects if theresistivity is not within the required range, including nonconformanceat the contact nip, poor toner releasing properties resulting in copycontamination, and generation of contaminant during charging. Otherproblems include resistivity that is susceptible to changes intemperature, relative humidity, running time, and leaching out ofcontamination to photoconductors. The substrate material andintermediate layer material preferably possess the desired resistivityenabling a field to be created for transfer, and discharge of the fieldbefore the next imaging cycle. The field created preferably is able totransfer dry toner or liquid ink from one substrate to another. Further,the preferred outer layer is preferably thin enough to create anddissipate a field, yet insulative enough to prevent electrical shortsfrom pin holes in transferring substrates. It is desired that thepolyimide layer and outer layers of the transfer or transfix films haveresistivity falling within the ranges disclosed above.

Preferably, a doped metal oxide is contained or dispersed in thepolyimide layer. Preferred doped metal oxides include antimony doped tinoxide, aluminum doped zinc oxide, antimony doped titanium dioxide,similar doped metal oxides, and mixtures thereof.

In a particularly preferred embodiment of the invention, the doped metaloxide is added to the polyimide layer in an amount of about 5 to about65 percent by weight of total solids, preferably from about 10 to about50 percent by weight of total solids, and particularly preferred of fromabout 10 to about 30 percent by weight of total solids. Total solids isdefined as the amount of polymer, filler(s), and any additives.

Other conductive fillers can be added to the polyimide layer. Examplesof additional conductive fillers include carbon blacks and graphite; andmetal oxides such as tin oxide, antimony dioxide, titanium dioxide,indium oxide, zinc oxide, indium oxide, indium tin trioxide, and thelike; and mixtures thereof. The additional filler (i.e., fillers otherthan doped metal oxide fillers) may be present in an amount of fromabout 1 to about 40 and preferably from about 4 to about 20 parts byweight of total solids.

In a preferred embodiment of the invention, the electrically conductivefiller is antimony doped tin oxide. Suitable antimony doped tin oxidesinclude those antimony doped tin oxides coated on an inert core particle(e.g., ZELEC® ECP-S, M and T) and those antimony doped tin oxideswithout a core particle (e.g., ZELEC® ECP-3005-XC and ZELEC®ECP-3010-XC). so ZELEC® is a trademark of DuPont Chemicals JacksonLaboratories, Deepwater, N.J. The core particle may be mica, TiO₂ oracicular particles having a hollow or a solid core.

In a preferred embodiment, the antimony doped tin oxides are prepared bydensely layering a thin layer of antimony doped tin oxide onto thesurface of a silica shell or silica-based particle, wherein the shell,in turn, has been deposited onto a core particle. The crystallites ofthe conductor are dispersed in such a fashion so as to form a denseconductive surface on the silica layer. This provides optimalconductivity. Also, the outer particles are fine enough in size toprovide adequate transparency. The silica may either be a hollow shellor layered on the surface of an inert core, forming a solid structure.

Preferred forms of antimony doped tin oxide are commercially availableunder the tradename ZELEC® ECP (electroconductive powders) from DuPontChemicals Jackson Laboratories, Deepwater, N.J. Particularly preferredantimony doped tin oxides are ZELEC® ECP 1610-S, ZELEC® ECP 2610-S,ZELEC® ECP 3610-S, ZELEC® ECP 1703-S, ZELEC® ECP 2703-S, ZELEC® ECP1410-M, ZELEC® ECP 3005-XC, ZELEC® ECP 3010-XC, ZELEC® ECP 1410-T,ZELEC® ECP 3410-T, ZELEC® ECP-S-X1, and the like. The structure of theZELEC® ECP powder includes fine crystallites of antimony doped tin oxidedensely layered onto the surface of a silica based particle. Thecrystallites of the conductor are dispersed in such a fashion that theyform a dense conductive surface on the silica layer, which insuresoptimal conductivity. The silica of the ZELEC® ECP may be structuredeither as a hollow shell or it may be layered on the surface of anotherinert core, making it a solid striker. There are three commercial gradesof ZELEC® ECP powders including an acicular, hollow shell product(ZELEC® ECP-S), an equiaxial titanium dioxide core product (ZELECECP-T), and a plate shaped mica core product (ZELEC® ECP-M). Thefollowing Tables demonstrate the product properties of ZELEC® ECP. Thisinformation was taken from a DuPont Chemicals Jackson Laboratories,Deepwater, N.J., product brochure.

                  TABLE 1    ______________________________________    Product Physical Properties (S, T & M)    Property   Core     Shape      Mean Part. Size    ______________________________________    ECP-S      Hollow   Acicular    3 microns    ECP-T      Solid    Equiaxial   1 micron    ECP-M      Solid    Platelike  10 microns    ______________________________________

                  TABLE 2    ______________________________________    Product Chemical Properties (S, T & M)    Property  ECP-S       ECP-T      ECP-M    ______________________________________    Bulk Density              0.4 gm/cc   1.0 gm/cc  0.6 gm/cc    Specific gravity              3.9 gm/cc   4.9 gm/cc  3.9 gm/cc    Surface area              50 m.sup.2 /gm                          20 m.sup.2 /gm                                     30 m.sup.2 /gm    Mean part. size              3 microns   1 micron   10 micron    Dry powder resist              2-30 ohm-cm 2-30 ohm-cm                                     20-300 ohm-cm    Core      Hollow      TiO.sub.2  Mica    ______________________________________

                  TABLE 3    ______________________________________    Product Properties (XC)    Property      3005-XC       3010-XC    ______________________________________    Antimony %    6.5           10    Bulk powder resist.                  .5 to 3 ohm-cm                                .5 to 3 ohm-cm    Specific gravity                  6.5 to 7.5 gm/cc                                6.5 to 7.5 gm/cc    Surface area  15 to 30 m.sup.2 /gm                                60 to 80 m.sup.2 /gm    Particle size (D50)                  .7 microns    2 microns    ______________________________________

Optionally, any known and available suitable adhesive layer may bepositioned between the polyimide substrate and the outer conformablelayer in the two layer configuration. An adhesive may be positionedbetween the polyimide substrate and the intermediateconformable/electrical layer and/or between the conformable/electricallayer and the release layer in the three layer configuration.

Examples of suitable adhesives include Dow Corning® A 4040 prime coat,which is especially effective when used with fluorosilicone layers, andDow Tactix® blends, Ciba-Geigy Araldite® MY-721 and Morton Thixon330/311, all of which are suitable for use with fluoropolymer andsilicone rubber layers. The adhesive may have the same electricalproperties as the substrate, polyimide or intermediate conformablelayer.

Additives and additional fillers may be present in any of theabove-described layers.

Specific embodiments of the invention will now be described in detail.These examples are intended to be illustrative, and the invention is notlimited to the materials, conditions, or process parameters set forth inthese embodiments. All parts are percentages by solid weight unlessotherwise indicated.

EXAMPLES Example 1

Single layer transfer material

A single layer resistive polyimide transfer material having an antimonydoped tin oxide filler dispersed therein were prepared. An antimonydoped tin oxide filler having the tradename ZELEC® 3005-XC availablefrom DuPont Chemicals Jackson Laboratories, Deepwater, N.J., was mixedwith a polyimide monomer (KAPTON® MT, available from DuPont) and themixture was milled to form a homogeneous dispersion. The homogeneousdispersion can be purchased from DuPont as DuPont designation 300PB. Theresulting dispersion was coated by extrusion onto a drum and thepolyimide monomers were allowed to crosslink into a thin film of fromabout 25 to about 150 microns thick.

The material was formed into a seamed belt using a puzzle cut seampattern with an adhesive. No appearance of markings on the paper due tofilm filler offsetting or coining was demonstrated. These markings arecommon with carbon black or graphite filled films. The surface of thefilm was exposed to fluorine gas to produce a fluorinated polyimide filmsurface. The surface energy was reduced to 28 dynes/cm. Initial tonerrelease from the film was complete. It was determined that this materialcan be used for smooth substrates and low density toner images.

Example 2

Two layer transfer material

A polyimide transfer material was prepared in accordance with Example 1with no surface fluorination. The polyimide material was coated with aDow Corning A 4040 primer adhesive and subsequently overcoated by areverse roll coating method with silicone rubber 552 (100 parts hydroxypolydimethyl siloxane with molecular weight of approximately 3500, 15parts ethyl silicate/ethyl alcohol, 60 parts iron oxide, 60 parts MEK,and 1 part dibutyl tin diacetate). Other samples of the polyimidematerial were coated with a fluoroelastomer (such as those availablefrom DuPont under the tradename VITON®), urethane, fluorosilicone andsilicone. After coating, the two layer configuration coatings were thencured through an air tunnel through a ramped temperature up to about250° C. for about 24 hours depending on the outer elastomer coatingmaterial. The coatings were measured to have a thickness of about 12 toabout 125 microns.

The polyimide/ZELEC® material coated with silicone rubber 522demonstrated an initial modulus of 300 PSI, a resistivity of about 10¹⁴ohms/sq and a surface energy of from about 21 to about 26 dynes/cm.

Example 3

Three layer transfer system

A three layer transfer belt was fabricated using the polyimide/ZELEC®material as prepared in Example I. A conformable VITON® E45 material(purchased from DuPont) was fabricated over the polyimide/ZELEC® to athickness of about 75 μm. This material had electrical propertiesequivalent to the base material and conformability to conform to roughpapers. A silicone elastomer known as 552 (polydimethyl siloxane withmolecular weight of approximately 3500 and filled with iron oxide)release layer was then overcoated to a thickness of approximately 25 μm.

The three layer system demonstrated a resistivity of 10¹⁰ ohms/sq and aninitial modulus of 500 PSI.

While the invention has been described in detail with reference tospecific and preferred embodiments, it will be appreciated that variousmodifications and variations will be apparent to the artisan. All suchmodifications and embodiments as may readily occur to one skilled in theart are intended to be within the scope of the appended claims.

We claim:
 1. A transfer film component comprising a polyimide film and electrically conductive doped metal oxide fillers dispersed therein, wherein said polyimide film has a surface resistivity of from about 10⁶ to about 10¹⁴ ohm/sq.
 2. The transfer film of claim 1, wherein said resistivity is from about 10⁸ to about 10¹³ ohm/sq.
 3. The transfer film of claim 1, wherein said conductive filler is antimony doped tin oxide.
 4. The transfer film of claim 1, wherein said conductive filler is present in an amount of from about 5 to about 65 percent by weight of total solids.
 5. The transfer film of claim 4, wherein said conductive filler is present in an amount of from about 10 to about 30 percent by weight of total solids.
 6. The transfer film of claim 1, wherein said polyimide is selected from the group consisting of aromatic polyimides, poly(amide-imide), polyetherimide, siloxane polyetherimide block copolymers and mixtures thereof.
 7. The transfer film of claim 6, wherein said polyimide is an aromatic polyimide selected from the group consisting of a) the reaction product of pyromellitic acid and diaminodiphenylether, b) the imidization product of a copolymeric acid of biphenyltetracarboxylic acid and pyromellitic acid with phenylenediamine and diaminodiphenylether, c) the reaction product of pyromellitic dianhydride and benzophenone tetracarboxylic dianhydride copolymeric acids with 2,2-bis(4-(8-aminophenoxy) phenoxy)-hexafluoropropane, d) polyimides comprising 1,2,1',2'-biphenyltetracarboximide and para-phenylene groups, and e) polyimides comprising biphenyltetracarboximide functionality with diphenylether end spacers.
 8. The transfer film of claim 1, wherein said polyimide is fluorinated.
 9. The transfer film of claim 1, further comprising an outer layer provided on said polyimide film.
 10. The transfer film of claim 9, wherein said outer layer comprises a material selected from the group consisting of fluoropolymers, polyimides and silicone rubbers.
 11. The transfer film of claim 10, wherein said outer layer comprises a fluoropolymer selected from the group consisting of polyfluoroalkoxypolytetrafluoroethylene, polytetrafluoroethylene, and fluorinated ethylenepropylene copolymer.
 12. The transfer film of claim 10, wherein said outer layer comprises a fluoroelastomer selected from the group consisting of a) copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, b) terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, and c) tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene and a cure site monomer.
 13. The transfer film of claim 1, further comprising an intermediate conformable layer on said polyimide film, and an outer release layer provided on said intermediate layer.
 14. The transfer film of claim 13, wherein said intermediate conformable layer has a hardness of from about 40 to about 90 Shore A.
 15. The transfer film of claim 13, wherein said intermediate conformable layer comprises a polymer selected from the group consisting of fluoropolymers, ethylene diene propene monomers, urethane nitrites, and silicone rubbers.
 16. The transfer film of claim 13, wherein said outer release layer comprises a polymer selected from the group consisting of fluoropolymers, silicone rubbers, and polyimides.
 17. The transfer film of claim 13, wherein said outer release layer further comprises a conductive filler selected from the group consisting of carbon black, boron nitride and metal oxides.
 18. The transfer film of claim 17, wherein said metal oxide conductive filler is iron oxide.
 19. The transfer film of claim 1, further comprising a heating element, wherein said film is in contact with said heating element in order to effect transfix capabilities to said transfer film.
 20. A bias transfer member for use in an electrostatographic printing apparatus for transferring electrically charged particles from an image support surface to said biasable transfer member, wherein said biasable transfer member comprises a polyimide film and electrically conductive doped metal oxide fillers dispersed therein, wherein said polyimide film has a surface resistivity of from about 10⁶ to about 10⁴ ohm/sq.
 21. The bias transfer member of claim 20, wherein said polyimide film is biased by a DC bias potential.
 22. The bias transfer member of claim 20, wherein said polyimide film is biased by a DC and an AC bias potential.
 23. An image forming apparatus for forming images on a recording medium comprising:a charge-retentive surface to receive an electrostatic latent image thereon; a development component to apply toner to said charge-retentive surface to develop said electrostatic latent image to form a developed image on said charge retentive surface; a transfer film component to transfer the developed image from said charge retentive surface to a copy substrate; said transfer film component comprising a polyimide film substrate and electrically conductive doped metal oxide fillers dispersed therein, wherein said polyimide film has a surface resistivity of from about 10⁶ to about 10¹⁴ ohm/sq.
 24. An image forming apparatus for forming images on a recording medium comprising:a charge-retentive surface to receive an electrostatic latent image thereon; a development component to apply toner to said charge-retentive surface to develop said electrostatic latent image to form a developed image on said charge retentive surface; a bias transfer film component for transferring electrically charged particles from said charge retentive surface to said bias transfer film component, wherein said bias transfer film component comprises a polyimide film substrate and electrically conductive doped metal oxide fillers dispersed therein, wherein said polyimide film has a surface resistivity of from about 10⁶ to about 10¹⁴ ohm/sq. 